SYSTEM AND METHOD FOR WIRELESS COMMUNICATIONS

• US 20090303006A1
• Filed: 06/06/2008
• Published: 12/10/2009
• Est. Priority Date: 06/06/2008
• Status: Active Grant

• Current Assignee: Lyngsoe Systems
• Original Assignee: Lyngsoe Systems
• Inventors: Eggers, Patrick Claus Friedrich, Pedersen, Gert Frolund, Oprea, Alex, Yanakiev, Boyan Radkov
• Granted Patent: US 8,149,093 B2
• Time in Patent Office: Days
• US Class Current: 340/10.100
• CPC Class Codes: H04Q 2209/47 using RFID associated with sensors
• CPC Class Codes: H04Q 2209/84 Measuring functions
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

A method of detecting position of a moving RFID tag relative to an antenna, includes continually receiving a signal from the RFID tag at the antenna. The phase of the received signal over a time period is detected and, based on a maximum detected phase, the position of the RFID tag relative to the antenna is detected.

Claims

1. An objects localization system consisting of backscattering tags attached to objects moving along a know unidirectional path and interrogators, wherein said interrogator comprises:

an antenna system to transmit and receive RF signals to/from tags;

a transmitter and a receiver using homodyne down-conversion;

a localization processor for providing tag position information wherein, said localization processor estimates the position of the tag based on phase measurement and comprise;

i) a phase detector;

ii) a power detector;

iii) a phase gradient null estimator;

iv) a position estimator

2. The localization processor of claim 1, wherein an Interrogator receives the signal backscattered by a tag with a single antenna, and wherein said phase gradient null estimator estimates the location of the zero phase gradient of the tag backscattered signal by performing the following algorithm:

first, the local phase jumps are found from the raw data and obvious outliers are detected;

then local instantaneous power relative to mean power around phase peaks is used to identify and filter the phase jumps (phase gradient transients) to smooth out the phase trajectory and further improve the gradient zero crossing detection and consequently the position of the tag

3. The localization processor of claim 2, wherein an Interrogator receives the signal backscattered by a tag with several antennae, and wherein said phase gradient estimator is used to identify the phase jumps (phase gradient transients) per antenna and combines the weighted information from several antennae to smooth out the phase trajectory and improve the combined phase gradient zero crossing detection and consequently the position of the tag

4. The phase peak estimator of claim 3, wherein said phase peak estimator uses a Kalman filter followed by a linear regression of the phase gradient to find the phase trajectory zero crossing that also identifies the antenna passing point. Higher order phase gradient can also be used for further input, like the 2^nd order derivate (phase curvature, will have a turn tangent at the passing point which can be detected).

5. The localization processor of claim 1, wherein at least one optical position sensor and one mechanical position sensor is used to further enhance position estimation

6. The localization processor of claim 1, wherein at least one acoustic/ultra-sound position sensor system is used to further enhance position estimation.

7. The localization processor of claim 1, wherein at least one weight position sensor is used to further enhance position estimation.

8. The interrogator of claim 1, wherein antennae are tilted to steer nulls to narrow the tag activation zone.

9. Collaborative antenna processing to achieves steering nulls steer to narrow the tag activation zone.

10. A method of detecting position of a moving RFID tag relative to an antenna, comprising:

continually receiving a signal from the RFID tag at the antenna;

detecting the phase of the received signal over a time period;

based on a maximum detected phase detecting the position of the RFID tag relative to the antenna.

11. A system for detecting position of a moving RFID tag relative to an antenna, comprising:

a receiver continually receiving a signal from the RFID tag via the antenna;

a phase detector detecting the phase of the signal;

a phase peak estimator determining a maximum detected phase thereby to detect the position of the RFID tag relative to the antenna.